The broad objective is to investigate the nature of speech sounds to find out why they are so effective for human communication and so readily learned by children. These properties of speech are traceable to its unique status as a phonological code, bearing the dual imprint of the processes by which it is produced and received, and pointing to the existence in man of special mechanisms for language in its heard and spoken forms. The case is otherwise for written language. The reading of it is learned less easily and later in the child's development -- and not always successfully. Hence, a second objective is to investigate the underlying relationships and dependencies between the processes of reading and listening. Studies of speech as a code will use both synthetic and natural speech in experiments on the acoustic cues for perception, dichotic listening to conflicting and compatible stimuli, and the discrimination of speech and nonspeech sounds. Further research on rules (programs) for the synthesis of speech will aim at a closer approximation to a true grammar of speech -- that is, a set of rules that model production processes and so rationalize the relation of phonological message to acoustic waveform. The acquisition of the speech code by children will be investigated, primarily in terms of what it is that is learned at various stages, or is already in the repertoire of the infant at a very early age. An alternate approach to innate capabilities lies in seeking common phonetic features across languages. These studies are underway here; those on children and infants are being done with colleagues in other laboratories. In studies of reading, the emphasis is on the linguistic level at which visual inputs merge into the special processes for speech. The techniques of visual information processing will be adapted to this purpose, supplemented by dichotic, dicoptic and cross-modal stimulus presentation under computer control.